mc68hc908gr16 Freescale Semiconductor, Inc, mc68hc908gr16 Datasheet - Page 179

• Manufacturer Part Number: mc68hc908gr16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

15.2 SIM Bus Clock Control and Generation
The bus clock generator provides system clock signals for the CPU and peripherals on the MCU. The
system clocks are generated from an incoming clock, CGMOUT, as shown in
originates from either an external oscillator or from the on-chip PLL.
15.2.1 Bus Timing
In user mode, the internal bus frequency is either the crystal oscillator output (CGMXCLK) divided by four
or the PLL output (CGMVCLK) divided by four.
15.2.2 Clock Startup from POR or LVI Reset
When the power-on reset module or the low-voltage inhibit module generates a reset, the clocks to the
CPU and peripherals are inactive and held in an inactive phase until after the 4096 CGMXCLK cycle POR
timeout has completed. The RST pin is driven low by the SIM during this entire period. The IBUS clocks
start upon completion of the timeout.
Freescale Semiconductor
PIN LOGIC
RESET
V
DD
INTERNAL
PULLUP
DEVICE
SIM RESET STATUS REGISTER
RESET PIN CONTROL
Figure 15-2. SIM Block Diagram
MC68HC908GR16 Data Sheet, Rev. 5.0
POR CONTROL
STOP/WAIT
CONTROL
CONTROL
AND PRIORITY DECODE
INTERRUPT CONTROL
CLOCK
CLOCK GENERATORS
RESET
COUNTER
SIM
÷ 2
CONTROL
MASTER
RESET
SIM Bus Clock Control and Generation
MODULE STOP
MODULE WAIT
CPU STOP (FROM CPU)
CPU WAIT (FROM CPU)
SIMOSCEN (TO CGM)
CGMXCLK (FROM CGM)
CGMOUT (FROM CGM)
INTERNAL CLOCKS
LVI (FROM LVI MODULE)
ILLEGAL OPCODE (FROM CPU)
ILLEGAL ADDRESS (FROM ADDRESS
MAP DECODERS)
COP (FROM COP MODULE)
INTERRUPT SOURCES
CPU INTERFACE
FORCED MONITOR MODE ENTRY
Figure
15-4. This clock
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